High surface area composition for use in the catalytic hydroconversion of a heavy hydrocarbon feedstock, a method making such composition and its use

ABSTRACT

A catalyst composition that is especially useful in the hydroconversion of pitch, micro carbon residue and sulfur contents of a heavy hydrocarbon feedstock without the excessive formation of sediment. The catalyst composition is a reasonably high surface area composition containing alumina and a low molybdenum content with a high ratio of nickel-to-molybdenum. The catalyst composition further has a unique pore distribution that in combination with the special metals loading provide for good conversion of pitch and micro carbon residue without an excessive yield of sediment.

This application claims the benefit of U.S. Provisional Application No.61/162,691 filed Mar. 24, 2009, the entire disclosure of which is herebyincorporated by reference.

The invention relates to a composition that is useful as a catalyst forthe catalytic hydroconversion of heavy hydrocarbon feedstocks, a methodof making such a composition and its use.

There is an ongoing effort to find improved catalyst compositions thatmay suitably be used in hydroprocessing of heavy hydrocarbon feedstocks.A desirable property of these catalyst compositions includes having highstability in catalytic activity when used in the hydroprocessing ofheavy hydrocarbon feedstocks. When these catalysts are used for thehydroconversion of heavy hydrocarbon feedstocks, it is desirable forthem to provide for a high conversion of the pitch component, which is aheavy boiling fraction of the heavy hydrocarbon feedstock, to lighterand more valuable components. This conversion of the heavy boilingfraction of a heavy hydrocarbon feedstock requires consumption ofhydrogen.

Disclosed in U.S. Pat. No. 5,616,530 (Sherwood, Jr. et al.) is animpregnated, alumina supported catalyst composition for use in thehydroprocessing of a heavy hydrocarbon feedstock. The catalyst includesan alumina support that is impregnated with a Group VIII metal (e.g.,nickel) and a Group VIB metal (e.g., molybdenum) and has a specifiedpore size distribution. The pore size distribution of the catalyst issuch that from 50% to 62.8% of the total pore volume is present in themicropores of diameter from 55 to 115 Å and from 20% to 30.5% of thetotal pore volume is present in the macropores of diameter greater thanabout 250 Å. Present in the large macropores of diameter from 500 to10,000 Å is from about 18 to 24% of the total pore volume. The metalloadings of the catalyst include a non-cobalt Group VIII metal oxide inan amount of from 2.5 to 6 wt. % and a Group VIB metal oxide in anamount of from 14.5 to 24 wt. %.

Disclosed in U.S. Pat. No. 5,498,586 (Dai and Sherwood, Jr.) is acatalyst composition consisting essentially of a porous alumina supportbearing 3 to 6 wt. % of a Group VIII metal oxide, 14.5 to 24 wt. % of aGroup VI-B, and 0 to 6 wt. % of a phosphorus oxide for use in thehydroprocessing of a heavy hydrocarbon feedstock. The catalyst has atotal pore volume of 0.5 to 0.75 cubic centimeters per gram (cc/g) and aspecified pore size distribution. The pore size distribution of thecatalyst is such that from 63% to 78% of the total pore volume ispresent in the micropores of diameter from 55 to 115 Å, from 0.12 cc/gto 0.16 cc/g of the total pore volume is present in large pores of adiameter greater than 160 Å and from 11% to 18% of the total pore volumeis present in the macropores of diameter greater than about 250 Å. Thetotal surface area of the catalyst is 240 square meters per gram (m²/g)to 310 m²/g.

U.S. Pat. No. 6,387,248 (Sherwood, Jr. et al.) discloses a relativelylow surface area catalyst composition having a specific pore sizedistribution and is made by co-mulling alumina, Group VIII metal saltand Group VIB metal salt and forming an extrudate of the mixture that issubjected to a relatively low temperature hydrothermal calcination. Thehydrothermal calcination is conducted in an atmosphere of air and steamand at a temperature of from about 1000° F. to 1150° F. The catalystcontains from about 1.1 to about 6 wt nickel oxide and from about 5 toabout 24 wt% molybdenum oxide. The pore size distribution of thecatalyst is such that less than about 20% of the total pore volume is asmicropores of diameter less than about 100 Å, at least about 34% of thetotal pore volume is as micropores of diameter in the range of fromabout 100 Å to 200 Å, and from about 26% to 46% of the total pore volumeis present as mesopores of diameter greater than or equal to 200 Å. Thecatalyst has a total surface area of 150 to 240 m²/g.

It is desirable for certain hydroprocessing catalysts to provide for thehigh conversion of the coke precursors of heavy hydrocarbon feedstocks,which are typically referred to as “Micro Carbon Residue,” or MCR, inorder to prevent or reduce fouling of downstream process equipment andto provide other benefits. It is undesirable in the hydroconversionprocesses to form sediment in the conversion product, and, thus, acatalyst composition that provides for the high conversion of a heavyfeedstock without incremental formation of sediment in thehydroconverted product is a much-desired property of the catalyst and ofthe process.

Accordingly, the inventive composition is a catalyst that has especiallyuseful properties in the hydroconversion of heavy hydrocarbonfeedstocks. This catalyst composition comprises a molybdenum componentin an amount of less than 11 wt. %, with the wt. % being based on thetotal weight of said catalyst composition and assuming said molybdenumcomponent is in the oxide form (MoO₃) regardless of its actual form, anda nickel component present in an amount such that said catalystcomposition has a weight ratio of said nickel component-to-saidmolybdenum component exceeding 0.25, with said weight ratio beingcomputed assuming said nickel component and said molybdenum componentare each in the oxide form (i.e., NiO/MoO₃) regardless of their actualforms, and wherein said catalyst composition has a total surface area inthe range of from 240 m²/g to 360 m²/g, a total pore volume of at least0.65 cc/g and a pore size distribution such that at least 10% of thetotal pore volume is present in macropores of diameter greater thanabout 250 Å.

The catalyst composition of the invention in one embodiment is made by amethod comprising mixing alumina powder, a nickel compound, and amolybdenum compound to provide a co-mulled mixture, comprising saidnickel compound, said molybdenum compound and alumina; forming anagglomerate of said co-mulled mixture; and calcinating said agglomeratein air without added steam under calcination conditions that include acalcination temperature exceeding 1150° F. to thereby provide saidcatalyst composition, wherein said catalyst composition contains amolybdenum component present therein in an amount of less than 11 wt. %,with the wt. % being based on the total weight of said catalystcomposition and assuming said molybdenum component is in the oxide form(MoO₃) regardless of its actual form, and a nickel component present insaid catalyst composition in an amount such that said catalystcomposition has a weight ratio of said nickel component-to-saidmolybdenum component exceeding 0.25, with said weight ratio beingcomputed assuming said nickel component and said molybdenum componentare each in the oxide form regardless of their actual forms, and whereinsaid catalyst composition has a total surface area in the range of from240 m²/g to 360 m²/g.

The catalyst composition of the invention can be used in a process forthe hydroconversion of a heavy hydrocarbon feedstock, wherein saidprocess comprises: contacting, under suitable hydroconversionconditions, said heavy hydrocarbon feedstock with the catalystcomposition.

The inventive catalyst composition is particularly useful in thehydroconversion of heavy hydrocarbon feedstocks. It has a high activitytoward the conversion of the pitch portion and the micro carbon residue(MCR) content of a heavy hydrocarbon feedstock while minimizingundesirable formation of sediment when the catalyst is used in thecatalytic hydroconversion of the heavy hydrocarbon feedstock.

One feature of the inventive catalyst composition is that it is acalcined particle, such as an agglomerated particle formed by, forexample, extrusion, pressing or balling techniques, of a co-mulledmixture of components that make up the catalyst composition. Thecomponents of the co-mulled mixture can comprise or consist essentiallyof alumina powder or powders, a nickel compound, a molybdenum compound,and, optionally, either phosphorus or catalyst fines, or both. In thepreparation of the co-mulled mixture, water or acid, or both, may alsobe co-mulled with the components and included as a component of theco-mulled mixture.

An important and essential feature of the inventive catalyst compositionis that it has relatively low molybdenum content but with a high weightratio of nickel-to-molybdenum (calculated as NiO/MoO₃ regardless oftheir actual forms). The inventive catalyst further has a relativelyhigh surface area and a specifically defined pore size distributionthat, in combination with the particular metal loadings of the catalystcomposition, can contribute to its catalytic properties of providing forhigh pitch and MCR conversion with a minimal amount of sedimentformation.

It has surprisingly been found that the inventive catalyst composition,having a low molybdenum concentration and a high weight ratio ofnickel-to-molybdenum, and those embodiments of the catalyst compositionthat have the particularly defined physical properties and porestructure, exhibits particularly good hydroconversion catalyticproperties. For instance, as mentioned above, the catalyst compositionprovides for a high conversion of pitch and MCR, and it also does thiswith a minimal amount of sediment formation. This particularly goodcatalytic performance of the low molybdenum content catalyst compositionis unexpected; because, one skilled in the art would normally expect toobserve a decline in catalytic performance with a decrease in themolybdenum content. This, however, is not observed with the inventivecatalyst composition.

Also, concerning the high nickel content of the catalyst compositionrelative to its molybdenum content, it has typically been viewed thatcatalyst performance tends to suffer with excessively high nickelcontent relative to the molybdenum content. The inventive catalystcomposition, however, includes both features in order to provide for thecatalytic benefits as described herein.

In one embodiment of the inventive catalyst composition, it is to have aspecifically defined pore size distribution that can be characterized asbeing bimodal in structure. It is believed that the particular porestructure of the catalyst composition in combination with itsspecifically defined metal loadings provides for the high pitch and MCRconversions with minimal formation of undesirable sediment.

One preferred embodiment of the inventive catalyst composition is thenon-impregnated form of the catalyst. This embodiment of the inventivecatalyst is non-impregnated in the sense that it is not made by theliquid phase impregnation of a preformed support material for thepurpose of incorporating the active metal components therein. Rather, inthis embodiment, the inventive catalyst composition is a co-mulledmixture of the principal components of the catalyst composition, whereinthe co-mulled mixture has been calcined at a relatively high calcinationtemperature in a gaseous atmosphere, such as air, that has had nosignificant addition of steam to the gaseous atmosphere.

In this embodiment, the co-mulling of the main components of thecatalyst composition provides several benefits over the preparation of acatalyst by impregnation methods. One of these benefits is that theco-mulled catalyst composition is more economical to make than animpregnated catalyst; because, several of the manufacturing stepsrequired for making an impregnated catalyst are not required for makingthe co-mulled catalyst. For instance, an impregnated catalyst requiresthe formation of a support particle that often must also be calcinedprior to its impregnation with metals. Once the support is impregnatedwith metals, it is then, typically, calcined a second time.

The co-mulled catalyst composition of the invention, on the otherhand,does not require an impregnation step nor does it require the priorpreparation of the support particle. A still further benefit of theco-mulled catalyst composition is that the co-mulling may contribute insome way to certain of the beneficial properties of the inventivecatalyst composition.

The molybdenum component is present in the calcined agglomerate of thecatalyst composition in an amount that is greater than or equal to 5 wt.% and in an amount that is less than 11 wt. %. It is desirable for themolybdenum component to be present in the calcined agglomerate in anamount in the range of from 6 wt. % to 11 wt. %. It is preferred,however, for the molybdenum component to be present in the calcinedagglomerate in an amount in the range of from 7.5 wt. % to 11 wt. %,more preferred, in the range of from 8 wt. % to 10 wt. %, and, mostpreferred, from 8.5 wt. % to 9.5 wt. %. These weight percents (wt. %)are based on the total weight of the calcined agglomerate (i.e., thetotal weight includes the sum of all the individual components of thecatalyst composition including the support material, metals, and anyother components) and assuming that the molybdenum component is presentin the oxide form, i.e., MoO₃, regardless of its actual form.

The nickel component is present in the calcined agglomerate of thecatalyst composition in an amount such that the weight ratio of thenickel component-to-molybdenum component is at least 0.25, with thisweight ratio being computed assuming each of the nickel and molybdenumcomponents being in their respective oxide forms (i.e., the weight ratioof NiO/MoO₃), regardless of their actual forms. It is desirable for thisweight ratio to be in the range of from 0.25 to 0.8. Preferably, theweight ratio of the nickel component-to-molybdenum component containedin the calcined agglomerate is in the range of from 0.27 to 0.52, and,most preferably, the weight ratio is from 0.34 to 0.42.

As noted above, the nickel-to-molybdenum ratio contained in theinventive catalyst composition is high. It is believed that thecombination of low molybdenum content and high nickel-to-molybdenumratio are critical features of the catalyst composition in that they, incombination with the specific pore structure and high surface area ofthe catalyst composition, provide for the unique catalytic performanceproperties of the inventive catalyst. It is quite unexpected that thecombination of these features provides for a catalyst composition thatis very active toward the high conversion of pitch and MCR of a heavyhydrocarbon feedstock but which causes a correspondingly low amount ofsediment formation; since, those skilled in the art would have thoughtthat a reduction in molybdenum content would tend to result in a lesscatalytically active catalyst and that a high relative nickel contentwould tend to interact with the molybdenum at the atomic and molecularlevels in undesirable ways.

The catalyst composition may also include a phosphorous component. Theamount of the phosphorous component in the catalyst composition can bein the range of from or about 0.0 wt. % to or about 6 wt. % (2.63 wt. %elemental phosphorous). Typically, the phosphorous component is presentin the catalyst composition in the range of from 0.5 wt % (0.22 wt. %elemental phosphorous) to 5 wt. % (2.19 wt. % elemental phosphorous),and, most typically, from 0.75 (0.33 wt. % elemental phosphorous) to 4wt % (1.75 wt. % elemental phosphorous). These weight percents (wt. %)are based on the total weight of the catalyst composition and assumingthat the phosphorous component is present in the oxide form, i.e., P₂O₅,regardless of the form that it is actually in.

As noted above in describing the critical features of the catalystcomposition, nickel is a necessary component of the catalystcomposition, and, in certain embodiments of the inventive catalystcomposition, it may further be desirable to exclude material amounts ofcertain of the other Group VIII metals (e.g., iron, cobalt, palladium,and platinum). In particular, in one specific embodiment of theinventive catalyst composition, it is desirable for the catalystcomposition to have a material absence of cobalt. What is meant byhaving a material absence of cobalt is that the catalyst compositioncontains no amount of cobalt that materially affects the performance ofthe catalyst composition.

Since it is believed that the significant presence of cobalt in thecatalyst composition with its low molybdenum content and high weightratio of nickel-to-molybdenum can negatively impact the catalyticeffectiveness of the catalyst composition when it is used inapplications involving the conversion of the pitch content of a heavyhydrocarbon feedstock, the cobalt should be absent from the catalystcomposition. Thus, it is best for the cobalt to be present in thecatalyst composition in an amount of no more than 0.1 wt. %, preferably,in an amount of no more than 0.05 wt. %, and, even in an amount of nomore than 0.01 wt. %, or even in a negligible amount.

Considering the effect that cobalt and certain other of the Group VIIImetals may have on the performance of the inventive catalystcomposition, the catalyst composition, as an alternative to one thatcomprises a molybdenum component, a nickel component, and alumina, mayconsist essentially of alumina, a molybdenum component, a nickelcomponent, and, optionally, a phosphorous component, all in theproportions and concentrations as described herein.

The catalyst composition of the invention has a relatively high totalsurface area, as determined by the nitrogen BET method, which is in therange of from 240 m²/g to 360 m²/g. A preferable range for the totalsurface area of the catalyst is from 250 m²/g to 350 m²/g, and, a morepreferable range is from 260 m²/g to 300 m²/g.

As earlier mentioned, the catalyst composition has a specificallydefined pore structure that, in combination with the particular metalloadings and other features of the catalyst composition, provides forthe minimization of the formation of sediment when used in thehydroconversion of a heavy hydrocarbon feedstock. This pore structure issuch that from 50% to 80% of the total pore volume of the catalyst ispresent as pores having a diameter in the range of from 55 Å to 115 Å,from 19.5% to 37% of the total pore volume of the catalyst is present aspores having diameters of greater than or equal to 160 Å, and from 11%to 30.5% of the total pore volume of the catalyst is present as poreshaving diameters of greater than or equal to 250 Å. In an embodiment ofthe invention, from 16% to 30% of the total pore volume of the catalystmay be present as pores having diameters greater than 500 Å, preferably,from 18% to 28% of the total pore volume is present as pores havingdiameters greater than 500 Å, and, most preferably from 19% to 26% ofthe total pore volume is present as pores having diameters greater than500 Å.

It is preferred for the percentage of total pore volume present as poresof diameter in the range of from 55 Å to 115 Å to be in the range offrom 55% to 70%, and, most preferred, from 50% to 62.8%.

As for the percentage of the total pore volume present as pores havingdiameters of greater than or equal to 160 Å, it is preferred to be inthe range of from 15.3% to 37%, and, most preferred, from 27.5% to 37%.

As for the percentage of the total pore volume present as pores ofhaving diameters of greater than or equal to 250 Å, it is preferred tobe in the range of from 11.8% to 30.5%, and, most preferred, from 20% to30.5%. The total pore volume of the catalyst composition is, generally,at least or greater than 0.65 cc/g, and, typically is in the range offrom 0.65 cc/g to 1.1 cc/g. More typically, the total pore volume is inthe range of from 0.7 cc/g to 1.05 cc/g, and, most typically, it is inthe range of from 0.75 cc/g to 1 cc/g.

The references herein to the pore size distribution and pore volume ofthe catalyst composition are to those properties as determined bymercury penetration porosimetry. The measurement of the pore sizedistribution of the catalyst composition is by any suitable mercuryporosimeter capable of working in the pressure range between atmosphericpressure and about 60,000 psi, using a contact angle of 130° with amercury surface tension of 474 dyne/cm at 25° C. Pore volume is definedas the total volume using the mercury intrusion method as measuredbetween atmospheric pressure and a pressure of about 60,000 psia.

In the co-mulled embodiment of the inventive catalyst composition, theco-mulled mixture of the starting materials or components of thecatalyst composition includes the components of alumina powder, a nickelcompound and a molybdenum compound. The starting components may alsoinclude a phosphorus compound or catalyst fines, or both, in addition tothe aforementioned alumina, nickel and molybdenum as well as water oracid, or both. The nickel compound may be introduced into the co-mulledmixture as an aqueous solution of a nickel salt. The molybdenum compoundmay also be introduced into the co-mulled mixture as an aqueous solutionof a molybdenum salt. A single solution containing both the nickelcompound and molybdenum compound may also be employed.

The co-mulled mixture is formed into particles, such as extrudates, thatare then calcined in air at a calcination temperature within a certainrange to thereby provide the final catalyst composition. It is believedthat this co-mulling may provide for a final catalyst having catalyticor physical, or both, properties that are distinguishable over those ofother hydroprocessing catalysts that have been prepared by a differentmethod, such as, for example, by impregnation.

The term “co-mulling” is used broadly in this specification to mean thatat least the recited starting materials are mixed together to form amixture of the individual components that is preferably substantiallyuniform or homogeneous. This term is intended to be broad enough inscope to include the mixing of the starting materials so as to yield apaste that exhibits properties making it capable of being extruded orformed into extrudate particles by any of the known extrusion methods.

The term “co-mulling” is also intended to encompass the mixing of thestarting materials so as to yield a mixture that is preferablysubstantially homogeneous and capable of being agglomerated into formedparticles, such as, extrudates, spheroids, pills or tablets, cylinders,irregular extrusions or merely loosely bound aggregates or clusters, byany of the methods known to those skilled in the art, including, but notlimited to, molding, tableting, pressing, pelletizing, extruding, andtumbling. The preferred method of agglomerating the mixture is byextrusion to form extrudate particles, typically, having diameters inthe range of from 0.3969 mm ( 1/64 inch) or 0.79375 mm ( 1/32 inch) to12.7 mm (1½ inch) and length to diameter ratios of from 0.2 to 3 or evenhigher.

Thus, the formation of the co-mulled mixture may be done by any methodor means known to those skilled in the art, including, but not limitedto, the use of such suitable types of solids-mixing machines astumblers, stationary shells or troughs, muller mixers, which are eitherbatch type or continuous type, and impact mixers, and the use of suchsuitable types of either batch-wise or continuous mixers for mixingsolids and liquids or for the formation of paste-like mixtures that areextrudable.

Suitable types of batch mixers include, but are not limited to,change-can mixers, stationary-tank mixers, double-arm kneading mixersthat are equipped with any suitable type of mixing blade.

Suitable types of continuous mixers include, but are not limited to,single or double screw extruders, trough-and-screw mixers and pug mills.

The mixing of starting materials used in the preparation of theco-mulled mixture may be conducted during any suitable time periodnecessary to properly homogenize the co-mulled mixture. Generally, theblending time may be in the range of upwardly to 12 or more hours.Typically, the blending time is in the range of from 0.1 hours to 3hours.

The alumina powder component used in the formation of the co-mulledmixture comprises particles of alumina. The alumina is preferablypredominantly in the pseudo-boehmite crystalline form (Al₂O₃.xH₂O wherex is an intermediate value between x=1 boehmite and x=3 gibbsite), withabout 20 wt. % to 30 wt. % water content, and is characterized as havinga median pore diameter by surface area from mercury porosimetry (with acontact angle of 140 degrees) in the range of from about 60 Å to about120 Å. The alumina is in a reasonably divided state so as to be in theform of a powder (when dry) that allows for its co-mulling or mixingwith the metal compounds, water and other constituents that make up theco-mulled mixture of the invention.

The alumina powder component may contain silica and, if silica ispresent, it is preferred for the alumina to contain less than 2 wt. %silica, and, most preferred, less than 1 wt. % silica. The alumina is ina reasonably divided state so as to be in the form of a powder (whendry) that allows for its co-mulling or mixing with the metal compounds,water and other constituents that make up the co-mulled mixture of theinvention.

The alumina particles of the alumina powder may be described in terms ofmesh size with most of the particles, i.e. at least 90 wt. % of theparticles, being able to pass through the mesh of a sieve No. 35(nominal sieve opening of 0.500 mm) and most of the particles, i.e., atleast 90 wt. % of the particles, not being able to pass through or beingretained by the mesh of a sieve No. 400 (nominal sieve opening of 0.037mm).

The nickel compound used in the preparation of the co-mulled mixture isany suitable nickel compound that is convertible to a nickel oxide formby calcination in air under the calcination conditions as definedherein. Possible suitable nickel compounds include nickel oxides, nickelcarbonates, nickel hydroxides, and nickel nitrates. One particularlysuitable nickel compound is nickel nitrate.

The molybdenum compounds used in the preparation of the co-mulledmixture can be molybdenum oxide and any other suitable molybdenumcompound that is convertible to a molybdenum oxide form by calcinationin air under the calcination conditions as defined herein. Possiblesuitable molybdenum compounds include molybdenum oxides, molybdenumoxide hydrates and molybdates. One particularly suitable molybdenumcompound is ammonium heptamolybdate.

To help control the macroporosity (as defined elsewhere herein) of thecatalyst composition, in one embodiment of the invention, the fines ofan already prepared hydroprocessing catalyst, that is preferably a freshor unused hydroprocessing catalyst, that contains nickel, molybdenum andphosphorous components supported on an alumina support is mixed orco-mulled along with the alumina powder, the nickel compound, themolybdenum compound, and, optionally, the phosphorus compound, acid andwater that form the co-mulled mixture. Fines from other types ofcatalysts or alumina supports may also be employed, including usedhydroprocessing catalyst that has been regenerated in full or in part ornot at all.

The fresh hydroprocessing catalyst from which the catalyst fines areprepared may be selected from commercially available hydroprocessingcatalyst products, which include typical impregnated catalysts, or itmay be obtained from the processing of the co-mulled catalystcomposition of the instant invention. The hydroprocessing catalyst fromwhich the catalyst fines are derived generally has a Group VI-Bhydrogenation metal content in the range of from 1 to 35 wt. %,calculated as trioxide (e.g., MoO₃), a Group VIII hydrogenation metalcontent in the range of from 1 to 10 wt. %, calculated as oxide (e.g.,NiO), and, optionally, a phosphorus content in the range upwardly to 10wt. %, calculated a P₂O₅. The hydroprocessing catalyst fines generallyhave a mean pore diameter in the range of from 40 Å to 150 Å.

To prepare the catalyst fines used in the blending with the othercomponents of the co-mulled mixture, the material (e.g., hydroprocessingcatalyst) is ground into a powder containing catalyst particles whereinat least 90 wt. % are able to pass through the mesh of a sieve No. 40(nominal sieve opening of 0.420 mm). Any suitable equipment known tothose skilled in the art that is capable of grinding the material intoparticles to form a powder may be used to prepare the catalyst fineswith average particle size between 5 and 50 microns (where onemicron=10⁻⁶ meters). An example of one such piece of equipment is aconventional hammer mill.

The amount of catalyst fines mixed with the other components of theco-mulled mixture is such as to help control the macroporosity of thefinal catalyst composition of the invention to within the desired rangesas described herein. Thus, the amount of catalyst fines contained in theco-mulled mixture can be in the range upwardly to 50 weight percent(i.e., from 0 wt. % to 30 wt. %) of the total weight, on a dry basis, ofthe alumina powder or powders and catalyst fines that make up thecatalyst. In other embodiments of the invention, the co-mulled mixturemay have from 1 wt. % to 40 wt. % catalyst fines based on the totalweight of the alumina powder and/or other powders of the catalyst, oreven from 5 wt. % to 30 wt. %.

The particles formed by agglomerating the co-mulled mixture are calcinedin air under suitable calcination conditions so as to provide the finalcatalyst composition of the invention. The calcination conditions shouldbe such as to convert the nickel and molybdenum compounds of theco-mulled mixture and agglomerate to oxide forms and to provide a finalcatalyst composition having the desired physical properties as describedherein.

The calcination of the agglomerate formed from the co-mulled mixture,preferably, should not be a hydrothermal-type calcination, which is anexposure of the agglomerate to an atmosphere of air with a significantpresence of steam at a reasonably high temperature. Rather, thecalcination of the agglomerate should be in the presence of an airatmosphere having no material or significant addition of steam. Thus,the calcination of the agglomerate may be conducted in an atmosphere ofair that has a concentration level of water that is typically observedin air at standard conditions, but there should be no material additionof water to the heated air beyond that which is naturally contained inair.

A material addition of water is an amount of water that is added to theheated air used in the calcination of the agglomerate that wouldmaterially affect the final properties of the calcined agglomerate orfinal catalyst composition of the invention.

An example of air that may suitably be used in the calcination of theagglomerate of the co-mulled mixture is air that is saturated with waterat a temperature of 60° F. and 1 atmosphere of pressure.

The calcination temperature should exceed 621° C. (1150° F.). Thepreferred range for the calcination temperature is from 635° C. (1175°F.) to 927° C. (1700° F.), and, a more preferred range for thecalcination temperature is from 649° C. (1200° F.) to 815° C. (1500°F.). The most preferred calcination temperature is in the range of from663° C. (1225° F.) to 815° C. (1500° F.).

The heavy hydrocarbon feedstock of the invention can be obtained fromany suitable source of hydrocarbons, including, for example, petroleumcrude oils and tar sand hydrocarbons, such as, heavy oils extracted fromtar sand. The heavy hydrocarbon feedstock can be a vacuum resid oratmospheric resid component of a petroleum crude oil or tar sandhydrocarbon. One potential source of the heavy hydrocarbon feedstock isfrom an oil sand, such as any of those that are recovered in many areasof Canada, that have been topped by atmospheric distillation and vacuumdistilled.

The heavy hydrocarbon feedstock can further include high concentrationsof sulfur and nitrogen compounds and metals, such as, nickel andvanadium. Indeed, it is the high concentrations of metal, sulfur andnitrogen compounds in addition to the high molecular weight of the heavyhydrocarbon feedstock that make its hydroprocessing so challenging.

The heavy hydrocarbon feedstock, thus, includes a mixture ofhydrocarbons derived from a crude oil or tar sand hydrocarbon materialor other source of heavy hydrocarbons. A major portion of the heavyhydrocarbons of the mixture has a boiling temperature exceeding about343° C. (650° F.). In addition, a portion, preferably a major portion,of the heavy hydrocarbons of the mixture has a boiling temperatureexceeding about 538° C. (1000° F.). The preferred heavy hydrocarbonfeedstock has a boiling range such that at least 50 weight percent boilsat a temperature exceeding 538° C. (1000° F.), and, most preferably, atleast 85 weight percent of the heavy hydrocarbon feedstock boils at atemperature exceeding 538° C. (1000° F.). The boiling ranges referencedherein are as determined by ASTM test procedure D-1160. The API gravityof the heavy hydrocarbon feedstock can range from about 0 to about 20,but, more specifically, the API gravity is in the range of from 3 to 15,and, more specifically, from 4 to 11.

The heavy hydrocarbon feedstock can also have a micro carbon residue(MCR) content, as determined by ASTM testing method D-4530, exceeding 10weight percent, and, more specifically, the MCR content exceeds 12weight percent, and, most specifically, it exceeds 14 weight percent. Apotential upper limit for the MCR content is less than 40 weightpercent.

The heavy hydrocarbon feedstock can also comprise sulfur compounds inamounts such that the concentration of sulfur in the heavy hydrocarbonfeedstock exceeds about 2 weight percent and even exceeds 3 weightpercent. More specifically, the sulfur concentration in the heavyhydrocarbon feedstock can be in the range of from 2 to 10 weightpercent, or from 4 to 10 weight percent.

The heavy hydrocarbon feedstock can further comprise nitrogen compoundsin amounts such that the concentration of nitrogen in the heavyhydrocarbon feedstock exceeds 0.1 weight percent and even exceeds 0.2weight percent. More specifically, the nitrogen concentration in theheavy hydrocarbon feedstock can be in the range of from 0.2 to 3 weightpercent.

As earlier noted, the metals contained in the heavy hydrocarbonfeedstock can include nickel or vanadium, or both. The nickelconcentration in the heavy hydrocarbon feedstock can exceed 10 parts permillion by weight (ppmw) or it can exceed 30 ppmw. More specifically,the nickel concentration in the heavy hydrocarbon feedstock can be inthe range of from 10 parts per million by weight (ppmw) to 500 ppmw, orfrom 40 to 500 ppmw.

The vanadium concentration in the heavy hydrocarbon feedstock can exceed50 ppmw or it can exceed 100 ppmw. More specifically, the vanadiumconcentration in the heavy hydrocarbon feedstock can be in the range offrom 50 ppmw to 1500 ppmw.

The process of the invention includes contacting the heavy hydrocarbonfeedstock, preferably in the presence of hydrogen, with the catalystcomposition of the invention under suitable hydroprocessing conditions.The inventive process provides for an exceptionally high percentageconversion of the pitch, MCR and sulfur contents of the heavyhydrocarbon feedstock.

While it is recognized that the term “pitch” may have differentdefinitions by and among hydroprocessing operators depending upon theirexperience and local custom, as the term is used in this specification,except as otherwise specified, and in the claims it refers to thehydrocarbon molecules contained in the fraction of the heavy hydrocarbonfeedstock that boil at temperatures above 538° C. (1000° F.). Thereferences herein to “pitch conversion” or similar references to theconversion of pitch, except as otherwise specified, are speaking of thecracking of the heavy hydrocarbon molecules that make up the pitchcomponent of the heavy hydrocarbon feedstock to smaller hydrocarbonmolecules that boil at temperatures below 538° C. (1000° F.).

The percent conversion of pitch is then defined as being the weightpercent of the pitch contained in the heavy hydrocarbon feedstock thatis converted by the hydroconversion process, and it can be representedby the ratio of the difference between the weight of pitch in a feed andthe weight of pitch in the product with the resulting difference beingdivided by the weight of pitch in the feed and the resulting ratio beingmultiplied by 100 to provide the percentage pitch conversion.

The percent conversion of MCR is defined as being the weight percent ofMCR contained in the heavy hydrocarbon feedstock that is converted bythe hydroconversion process, and it can be represented by the ratio ofthe difference between the MCR in a feed and the MCR in the product withthe resulting difference being divided by the MCR in the feed and theresulting ratio being multiplied by 100 to provide the percentage MCRconversion.

The percent sulfur conversion is defined in a similar manner as are thepitch conversion and MCR conversion in that it is the weight percent ofsulfur that is contained in the heavy hydrocarbon feedstock that isconverted by the hydroconversion process. Sulfur conversion can berepresented by the ratio of the difference between the weight of sulfurin a feed and the weight of sulfur in the product with the resultingdifference being divided by the weight of sulfur in the feed andresulting ratio being multiplied by 100 to provide the percentage sulfurconversion.

The hydroconversion process can be carried out by the use of anysuitable reaction means or system including fixed bed, moving bed,fluidized bed and ebullated bed reactor systems. While the inventivecatalyst composition can be used as a part of any suitable reactorsystem, its properties make it particularly suitable for use inebullated bed systems.

The hydroprocessing conditions under which the heavy hydrocarbonfeedstock is contacted with the hydroconversion catalyst composition ofthe invention include those process conditions that are effective inproviding for a hydrotreated product and, preferably, that are effectivein the conversion of a significant portion of the pitch and MCRcomponents of the heavy hydrocarbon feedstock but with a minimumformation of sediment.

The conversion of the pitch component can exceed about 50 weight percentof the pitch. A higher pitch conversion is desirable and, thus,preferably, pitch conversion exceeds 55 weight percent, and, mostpreferably, pitch conversion exceeds 60 weight percent.

Sediment is considered herein to be that as measured by testing a sampleby the Shell Hot Filtration Test (SHFT). See Jour. Inst. Pet. (1951),Volume 37, pages 596-604, “Determination of Dry-Sludge Content of FuelOils: Development of the Shell Hot Filtration Test (SHFT), by vanKerkvoort et al., which is incorporated herein by reference. Thesediment content of the hydroconversion product resulting from thehydroprocessing of the heavy hydrocarbon feedstock using the inventivecatalyst composition is typically lower than that expected forconventional hydroprocessing catalyst.

Suitable hydroprocessing conditions under which the heavy hydrocarbonfeedstock is contacted with the hydroconversion catalyst composition ofthe invention can include a hydroconversion contacting temperature inthe range of from about 300° C. (572° F.) to about 700° C. (1292° F.), ahydroconversion total contacting pressure in the range of from about 500psia to about 6,000 psia, which includes a hydrogen partial pressure inthe range of from about 500 psia to about 3,000 psia, a hydrogenaddition rate per volume of heavy hydrocarbon feedstock in the range offrom about 500 SCFB to about 10,000 SCFB, and a hydroconversion liquidhourly space velocity (LHSV) in the range of from about 0.2 hr ¹ to 5 hr1.

The preferred hydroconversion contacting temperature is in the range offrom 310° C. (590° F.) to 650° C. (1202° F.), and, most preferred, from316° C. (600° F.) to 600° C. (1112° F.).

The preferred hydroconversion total contacting pressure is in the rangeof from 500 psia to 3,000 psia, most preferably, from 1,000 psia to2,850 psia, with a preferred hydrogen partial pressure of from 800 psiato 2,000 psia, and most preferred, from 1,000 psia to 1,850 psia.

The LHSV is preferably in the range of from 0.2 hr⁻¹ to 4 hr⁻¹, and,most preferably, from 0.2 hr⁻¹ to 3 hr⁻¹. The hydrogen addition rate ispreferably in the range of from 600 SCFB to 8,000 SCFB, and, morepreferably, from 700 SCFB to 6,000 SCFB.

The unique properties of the inventive catalyst composition allow for asignificant improvement in the operation of existing hydroconversionprocess systems by the replacement of the catalyst that has been used insuch systems with the inventive catalyst composition that exhibits theabove-described enhanced hydroconversion properties.

The following Examples are presented to illustrate the invention, butthey should not be construed as limiting the scope of the invention.

EXAMPLE 1

This Example 1 describes the preparation of the inventive catalyst andthe comparison catalysts that were tested for performance as describedin Example 2.

Catalyst A

A co-mulled mixture was prepared by mixing in a muller mixer 2721.6parts (2049.4 on a dry basis) wide pore alumina powder and 594.3 parts(563.5 on a dry basis) green catalyst fines with a molybdenum componentmixture of 539.1 parts ammonium heptamolybdate (27% MoO₃) and 1406.2parts water and a nickel component mixture of 333.3 parts nickel nitratesolution, 81.1 parts 70% nitric acid and 1406.2 parts water. Thecomponents where mulled for 30 minutes followed by the addition of 14.1parts flocculant (Superfloc LMW 300) followed by another 5 minutes ofmixing. The co-mulled mixture was then extruded into extrudates thatwere dried in air at an approximate temperature of 250° F. for about 1hour. Thereafter, the dried extrudates were calcined in air for 1 hourat a temperature of 1370° F.

Catalyst B

A co-mulled mixture was prepared by mixing in a muller mixer 2721.6parts (2049.4 on a dry basis) wide pore alumina powder and 579.9 parts(549.9 on a dry basis) green catalyst fines with a molybdenum componentmixture of 342.8 parts ammonium heptamolybdate (27% MoO₃) and 1428.8parts water and a nickel component mixture of 325.3 parts nickel nitratesolution, 79.1 parts 70% nitric acid and 1428.8 parts water. Thecomponents where mulled for 30 minutes followed by the addition of 13.7parts flocculant (Superfloc LMW 300) followed by another 5 minutes ofmixing. The co-mulled mixture was then extruded into extrudates thatwere dried in air at an approximate temperature of 250° F. for about 1hour. Thereafter, the dried extrudates were calcined in air for 1 hourat a temperature of 1400° F.

Comparison Catalyst

The Comparison Catalyst was made in an analogous way to Catalysts A andB in commercial equipment. The Comparison Catalyst sample was made so asto have the same Total Surface Area and pore size distribution as thecatalysts of the instant invention and the same low Mo content(calculated as MoO3) as the catalysts of the instant invention, but witha relatively low nickel oxide to molybdenum oxide ratio (calculated asNiO/MoO3) compared to the catalysts of the instant invention. Presentedin Table 1 are the metal loadings of the inventive catalysts (Catalyst Aand Catalyst B) and of the Comparison Catalyst. Presented in Table 2 arethe pore structure details concerning the inventive and comparisoncatalysts.

TABLE 1 Composition of Inventive Catalyst (Catalyst A and Catalyst B)and the comparison catalysts (Comparison Catalyst). Comparative CatalystCatalyst Component Catalyst A B Ni (wt. %) 1.54 2.4 2.4 NiO (wt. %) 2.03.0 3.1 Mo (wt. %) 7.17 6.1 4.8 MoO₃ (wt. %) 10.8 9.2 7.2 NiO/MoO₃ (wtratio) 0.18 0.33 0.43 P (wt. %) 0.5 0.4 0.4 P₂O₅ (wt. %) 1.2 0.9 0.9 Sias SiO₂ (wt. %) 0.2 0.05 ≦0.05

TABLE 2 Physical Parameters of Inventive Catalyst (Catalyst A andCatalyst B) and comparison catalyst (Comparison Catalyst). ComparativeCatalyst Catalyst Property Catalyst A B N₂ surface area (m²/g) 277.3 271272 Hg Porosimetry % Total Pore Volume as 57.8 59.0 63.4 pores 55 to 115Å % Total Pore Volume as 33.6 31.3 28.0 pores greater than 160 Å % TotalPore Volume as 29.0 26.3 23.5 pores greater than 250 Å Total Pore Volume(cc/g) 0.87 0.90 0.90 % Total Pore Volume as 3.5 4.0 3.8 pores 250-500 Å% Total Pore Volume as 49.5 51.3 57.2 pores 50-100 Å % Total Pore Volumeas 19.4 19.7 16.7 pores 100-200

EXAMPLE 2

This Example 2 describes the experimental testing procedure andconditions use to test the catalysts described in Example 1 for theirhydroconversion performance.

Each of the catalysts was tested for its catalytic performance in thehydroprocessing and hydroconversion of a heavy hydrocarbon feed. Theheavy hydrocarbon feed used in the performance test was Arabian Mediumvacuum residue with properties as follow: density of 1.0347 g/cc; sulfurcontent of 5.3 wt. %; nitrogen content of 0.38 wt. %; MCR content of20.8 wt. %; and a pitch content (pitch is defined in this Example 2 tobe those hydrocarbons having a boiling temperature greater than 538° C.or 1000° F.) of 88.0 wt. %.

The tests were conducted in a simulated two-stage ebullated bed unitthat consisted of two continuous stirred tank reactor (CSTR) unitsobtained from Autoclave Engineers and equipped with Robinson-Mahoneyinternals connected together in series flow. Each reactor was loadedwith 51 cc of catalyst. The operating conditions included an operatingpressure of about 2250 psi, an operating temperature of 424° C. (795°F.), a liquid hourly space velocity of about 0.55 cc of feed per cc ofcatalyst per hour, and a hydrogen-to-oil ratio of about 4100 SCF/bbl.

The following Table 3 presents the results from the testing of theComparison Catalyst, Catalyst A and Catalyst B.

TABLE 3 Conversion Performance Results from the Testing of InventiveCatalyst and Comparison Catalyst Comparative Catalyst Catalyst CatalystA B Pitch Conversion, vol. % 72.4 74.8 67.4 MCR Conversion, wt. % 70 7166 S Conversion, wt. % 81 82 79 343° C.+ (650° F.+) SHSFT 0.07 0.05 0.06Sediment, wt. %

As may be observed from the data of Table 3, Catalyst A provides for animprovement in the conversion of pitch, micro carbon residue removal andsulfur removal while maintaining excellent control of sediment asmeasured by the Shell Hot Filtration Test (SHFT) on the product fractionboiling above 343° C. (650° F.). The data suggest that there is anoptimum in the required nickel-to-molybdenum ratio and in the molybdenumcontent of the inventive catalyst.

Example 3

This Example 3 describes the preparation of the inventive catalyst andthe comparison catalysts that were tested for performance as describedin Example 4.

Catalyst C

A co-mulled mixture was prepared by mixing in a muller mixer 4082.6parts (3074.2 on a dry basis) alumina powder and 891.5 parts (845.4 on adry basis) catalyst fines with a molybdenum component mixture of 808.8parts ammonium heptamolybdate (27% MoO₃) and 2109.2 parts water and anickel component mixture of 500.0 parts nickel nitrate solution, 121.6parts 70% nitric acid and 2109.2 parts water. The components wheremulled for 30 minutes followed by the addition of 21.1 parts flocculant(Superfloc LMW 300) followed by another 5 minutes of mixing. Theco-mulled mixture was then extruded into extrudates that were dried inair at an approximate temperature of 250° F. for about 1 hour.Thereafter, the dried extrudates were calcined in air for 1 hour at atemperature of 1370° F.

Catalyst D

A co-mulled mixture was prepared by mixing in a muller mixer 2721.4parts (2046.5 on a dry basis) alumina powder and 614.1 parts (572.6 on adry basis) catalyst fines with a molybdenum component mixture of 576.4parts ammonium heptamolybdate (27% MoO₃) and 1360.8 parts water and anickel component mixture of 495.7 parts nickel nitrate solution, 82.4parts 70% nitric acid and 1360.8 parts water. The components wheremulled for 30 minutes followed by the addition of 14.3 parts flocculant(Superfloc LMW 300) followed by another 5 minutes of mixing. Theco-mulled mixture was then extruded into extrudates that were dried inair at an approximate temperature of 250° F. for about 1 hour.Thereafter, the dried extrudates were calcined in air for 1 hour at atemperature of 1325° F.

A Second Comparison Catalyst

The Second Comparison Catalyst was made in an analogous way to CatalystsC and D in commercial equipment. The Comparison Catalyst sample was madeso as to have the same Total Surface Area and pore size distribution asthe catalysts of the instant invention and the same low Mo content(calculated as MoO₃) as the catalysts of the instant invention, but witha relatively low nickel oxide to molybdenum oxide ratio (calculated asNiO/MoO₃) compared to the catalysts of the instant invention.

Presented in Table 4 are the metal loadings of two inventive catalysts(Catalysts C and D) and the Second Comparison Catalyst. Presented inTable 5 are the pore structure details concerning the inventive andcomparison catalysts.

TABLE 4 Composition of Inventive Catalysts C and D and the SecondComparison Catalyst. Second Comparative Catalyst Catalyst ComponentCatalyst C D Ni (wt. %) 1.5 2.34 2.85 NiO (wt. %) 1.9 3.0 3.6 Mo (wt. %)6.8 5.99 5.96 MoO₃ (wt. %) 10.2 9.0 8.9 NiO/MoO₃ (wt ratio) 0.19 0.330.41 P (wt. %) 0.48 0.39 0.57 P₂O₅ (wt. %) 1.1 0.9 1.3 Si as SiO₂ (wt.%) 0.1 0.26 0.52

TABLE 5 Physical Parameters of Inventive Catalysts C and D and theSecond Comparison Catalyst. Second Comparative Catalyst CatalystProperty Catalyst C D N₂ surface area (m²/g) 254 272 260 Hg Porosimetry% Total Pore Volume as 59.0 60.4 60.6 pores 55 to 115 Å % Total PoreVolume as 32.6 30.5 29.7 pores greater than 160 Å % Total Pore Volume as28.5 25.9 24.9 pores greater than 250 Å Total Pore Volume (cc/g) 0.870.88 0.87 % Total Pore Volume as 3.3 3.7 4.0 pores 250-500 Å % TotalPore Volume as 52.5 54.2 53.2 pores 50-100 Å % Total Pore Volume as 16.717.1 19.3 pores 100-200 Å

Example 4

This Example 4 describes the experimental testing procedure andconditions use to test the catalysts described in Example 3 for theirhydroconversion performance.

Each of the catalysts was tested for its catalytic performance in thehydroprocessing and hydroconversion of a heavy hydrocarbon feed. Theheavy hydrocarbon feed used in the performance test was a 95/5 weightper weight blend of Bitumen vacuum residue from Canadian Oil Sands andHeavy Aromatic Oil with properties as follow: density of 1.0457 g/cc;sulfur content of 5.8 wt. %; nitrogen content of 0.62 wt. %; MCR contentof 18.2 wt. %; and a pitch content (pitch is defined in this Example 4to be those hydrocarbons having a boiling temperature greater than 524°C. or 977° F.) of 91.3 wt. %.

The tests were conducted in a simulated two-stage ebullated bed unitthat consisted of two continuous stirred tank reactor (CSTR) unitsobtained from Autoclave Engineers and equipped with Robinson-Mahoneyinternals connected together in series flow. Each reactor was loadedwith 56 cc of catalyst. The operating conditions included an operatingpressure of about 2010 psi, an operating temperature of 414° C. (778°F.), a liquid hourly space velocity of about 0.50 cc of feed per cc ofcatalyst per hour, and a hydrogen-to-oil ratio of about 3600 SCF/bbl.

The following Table 6 presents the results from the testing of a SecondComparison Catalyst, Catalyst C and Catalyst D. Catalysts C and Dprovide for an improvement in the conversion of pitch, micro carbonresidue removal and sulfur removal while maintaining excellent controlof sediment as measured by the Shell Hot Filtration Solids Test (SHFST)on the product fraction boiling above 390° C. (734° F.). The dataconfirms the advantage of the required nickel-to-molybdenum ratio.

TABLE 6 Conversion Performance Results from the Testing of the TwoAdditional Inventive Catalysts and Second Comparison Catalyst SecondComparative Catalyst Catalyst Catalyst C D Pitch Conversion, vol. % 72.272.7 75.3 MCR Conversion, wt. % 71.7 73.8 74.7 S Conversion, wt. % 87.688.3 89.0 390° C.+ (734° F.+) SHSFT 0.11 0.01 0.03 Sediment, wt. %

1. A catalyst composition comprising a molybdenum component in an amountof less than 11 wt. %, with the wt. % being based on the total weight ofsaid catalyst composition and assuming said molybdenum component is inthe oxide form (MoO₃) regardless of its actual form, and a nickelcomponent present in an amount such that said catalyst composition has aweight ratio of said nickel component-to-said molybdenum componentexceeding 0.25, with said weight ratio being computed assuming saidnickel component and said molybdenum component are each in the oxideform regardless of their actual forms, and wherein said catalystcomposition has a total surface area in the range of from 240 m²/g to360 m²/g, a total pore volume of at least 0.65 cc/g and a pore sizedistribution such that at least 10% of the total pore volume is presentin macropores of diameter greater than about 250 Å.
 2. A catalystcomposition as recited in claim 1, having a pore size distribution suchthat from 50% to 80% of the total pore volume of said catalystcomposition is present as pores having diameters in the range of from 55Å to 115 Å, from 19.5% to 37% of the total pore volume of said catalystcomposition is present as pores having diameters of greater at least 160Å, and from 11% to 30.5% of the total pore volume of said catalystcomposition is present in macropores of diameter greater than 250 Å. 3.A catalyst composition as recited in claim 2, wherein the catalystcomposition is prepared by mixing alumina powder, a nickel compound, anda molybdenum compound to provide a co-mulled mixture, comprising saidnickel compound, said molybdenum compound and alumina; forming anagglomerate of said co-mulled mixture; and calcining said agglomerate inair without added steam under calcination conditions that include acalcination temperature exceeding 1150° F. to thereby provide saidcatalyst composition.
 4. A catalyst composition as recited in claim 3,having a total pore volume and a pore diameter distribution whereby from50% to 80% of the total pore volume of said catalyst composition ispresent as pores of diameter in the range of from 55 Å to 115 Å, from11% to 30.5% of the total pore volume of said catalyst composition ispresent as pores having diameters of greater than or equal to 160 Å, andfrom 16% to 30% of the total pore volume of said catalyst composition ispresent in pores of diameter greater than 500 Å.
 5. A catalystcomposition as recited in claim 4, wherein said mixing step furtherincludes mixing calcined catalyst fines with said alumina powder, saidnickel compound, and said molybdenum compound to thereby form saidco-mulled mixture, wherein said co-mulled mixture includes an amount ofsaid calcined catalyst fines so as to provide for a desiredmacroporosity of said catalyst composition.
 6. A catalyst composition asrecited in claim 5, wherein said catalyst composition has a surface areain the range of from 250 to 350 m²/g, and said total pore volume in therange of from 0.65 to 1.1 cc/g.
 7. A catalyst composition as recited inclaim 6, wherein said molybdenum component is present in said catalystcomposition in the range of from 8 wt. % to 10 wt. % and said weightratio of said nickel component-to-said molybdenum component is in therange of from 0.27 to 0.8.
 8. A catalyst composition, comprising: acalcined agglomerate of a co-mulled mixture of alumina powder, a nickelcompound, and a molybdenum compound, wherein said calcined agglomeratecomprises: a molybdenum component present in an amount of less than 11wt. %, wherein the wt. % is based on the total weight of said calcinedagglomerate and assuming said molybdenum component is in the oxide form(i.e., MoO₃) regardless of its actual form; and a nickel componentpresent in said calcined agglomerate in an amount such that saidcalcined agglomerate has a weight ratio of said nickel component-to-saidmolybdenum component exceeding 0.25, wherein said weight ratio iscomputed assuming said nickel component and said molybdenum componentare each in their oxide form (i.e., NiO and MoO₃) regardless of theiractual forms, and wherein said calcined agglomerate has a total surfacearea in the range of from 240 m²/g to 360 m²/g.
 9. A catalystcomposition as recited in claim 8, wherein said catalyst composition hasa total pore volume and a pore diameter distribution whereby from 50% to80% of the total pore volume of said catalyst composition is present aspores of diameter in the range of from 55 Å to 115 Å, from 11% to 30.5%of the total pore volume of said catalyst composition is present aspores having diameters greater than or equal to 160 Å, from 16% to 30%of the total pore volume of said catalyst composition is present aspores having diameters of greater than 500 Å.
 10. A catalyst compositionas recited in claim 9, wherein said catalyst composition has a surfacearea in the range of from 250 to 350 m²/g; and said total pore volume isin the range of from 0.65 to 1.1 cc/g.
 11. A catalyst composition asrecited in claim 10, wherein said co-mulled mixture further includes aportion thereof calcined catalyst fines blended therein to provide adesired macroporosity.
 12. A catalyst composition as recited in claim11, wherein the heat-treatment of said agglomerate includes calcining ofsaid co-mulled mixture at a calcination temperature in the range of from635° C. (1175° F.) to 927° C. (1700° F.)
 13. A method of making acatalyst composition, wherein said method comprises: mixing aluminapowder, a nickel compound, and a molybdenum compound to provide aco-mulled mixture; forming an agglomerate of said co-mulled mixture; andheat-treating said agglomerate to provide said catalyst composition,wherein an amount of said alumina powder, an amount of said nickelcompound and an amount of said molybdenum compound provided in saidmixing step are such that said catalyst composition contains amolybdenum component present therein in an amount of less than 11 wt. %,with the wt. % being based on the total weight of said catalystcomposition and assuming said molybdenum component is in the oxide form(MoO₃) regardless of its actual form, and a nickel component present insaid catalyst composition in an amount such that said catalystcomposition has a weight ratio of said nickel component-to-saidmolybdenum component exceeding 0.25, with said weight ratio beingcomputed assuming said nickel component and said molybdenum componentare each in the oxide form regardless of their actual forms, and whereinsaid catalyst composition has a total surface area in the range of from240 m²/g to 360 m2/g.
 14. A process for the hydroconversion of a heavyhydrocarbon feedstock, wherein said process comprises: contacting undersuitable hydroconversion conditions said heavy hydrocarbon feedstockwith a catalyst composition as recited in claims 1 through 12.